Study On The Environmental Degradation Products (TFA) Of The ODS Replacements

This study was focused on the determination of trace trifluoroacetic acid(TFA) with derivation-gas chromatography. Conditions for both methods were optimized after the best derivative method was established. Methodologies of the two pretreatment methods were also studied.Acidified methanol was used as the derivative agent before TFA was detected with GC-ECD. Several factors were changed to investigate their effects on the esterification efficiency, including the bath temperature, the bath time, and the solvent volume. The best experimental conditions were as follows:samples were bathed at temperature of 50℃for 0.5h, the solvent volume of MTBE and acidified methanol were 2mL and 2mL. The best chromatography conditions were as follows:injector temperature was 220℃, split ratio was 1:5. GC programed was 30℃initial held for 5 minutes, programed at 30℃/min to 150℃, then 20℃/min to260℃, held for 2 min. Detector temperature was 350℃, carrier gas velocity was 1.0mL/min.Water sample was concentrated by rotary evaporation in the high concentration-liquid-liquid microextraction method. The pH, salt effect, extraction time were optimized to obtain the highest extraction efficiency. The best extraction conditions were as follows:2mL concentrated sulfuric acid and 18g anhydrous sodium sulfate were added in the samples before extraction. The linear range of this method was 3.84μg/L-76.76μg/L, relative standard deviation was less than 0.060, and the recovery rate was between 91.5%～105.9%.As comparison, solid-phase extraction (SPE) was also studied in this research. MAX cartridge (copolymer bonded with quaternary ammonium) was used in SPE. It was activated by the sequential addition of 5mL acetone,5mL methanol,5mL of reagent water,5mL 0.1M NaOH,5mL of reagent water. It was then washed with 2mL of MTBE and 2mL of acidified methanol after sample filtration. The results exhibited a good method performance. The linear range of this method was 76.76ng/L～15351ng/L, relative standard deviation was less than 0.047, and the recovery rate was between 95.1%～104.4%.Finally, parts of the lake water in Nanjing were tested to study the migration and behavior of TFA in environmental water bodies. As the experiments showed, the contents of TFA in these water bodies were between 1.34μg/L tol3.68μg/L. TFA was also detected in phytoplankton in some water bodies. The monitoring data of simulated water bodies indicated that the content of TFA reduced at first, then increased sharply, and decreased finally. The migration or degradation of TFA changed with the existence of sediment water.